The present invention relates to a pressure detection device for detecting pneumatic pressure in an intake manifold of an internal combustion engine.
In engine control systems for controlling the combustion of a fuel, by using a digital computer, in accordance with the pneumatic pressure in the intake manifold (hereinafter referred to as the intake manifold pressure) and with other engine parameters indicative of the condition of the engine, a pressure detection device must be provided for generating an electrical signal which corresponds to the intake manifold pressure. As an example, such a device is desirable in fuel injection control systems for controlling the amount of fuel to be injected into the engine in accordance with the intake manifold pressure and with the rotational speed of the engine.
A conventional pressure detection device is composed of only a pressure transducer for converting the intake manifold pressure to an electrical signal, and thus the converted electrical signal directly appears as a detected intake manifold pressure signal. The digital computer takes samples of the output signal from the pressure detection device at predetermined intervals of time, and then calculates, for example, the amount of fuel to be injected into the engine, in accordance with the samples taken.
However, according to the conventional pressure detection device, since the output signal from the pressure detection device changes in response to the pulsation of the intake manifold pressure, which pressure pulsation is caused by the intake stroke action and the compression stroke action of the engine, the samples of the signals taken differ from each other in value in accordance with the time when the samples are taken. Therefore, errors in the calculated amount of fuel to be injected into the engine occur. In particular, in a high rotational speed region, since the pulsation frequency of the intake manifold pressure becomes higher, the above error increases.